US2203903A - Stabilized photographic fixing powder - Google Patents

Description

Patented June e v v n v v Claims. This invention relates to en ompa es i i Photographic fixers dependpr il 1 3 thiosulfate, althoughdother thiosulfates such as I amrnonium andpotassium thiosuliates maybe i i used. In addition to the thiosulfate whichperforms theprimary dissolving action, photographl ic fixing baths usually containlsodium sulfite, a

suitable acid and a material for hardening gela- 1 tin in order to render the gelatin emulsions of films, plates or photographic paperaqhardand tough] Usuallythe acid employedf to imparta suitable pH is acetic acid, and sometimeslbuffers such aslcitricacid and the like may be usedt -[One of the serious disadvantages of the ordinary 1xingbaths isfthat they have relativelypoorkeeping ,qualities, particularly whenexposed to light or heat. There isa seriousn tendency towards de composition ofthe thiosulfate with formation of v as this has taken place, theflxings solution has to be "discarded although the thiosulfateimay not i be totally exhausted. Because of theifact that many amateur photographers do not process large quantities of photographic 'materialy at;,?. time; the lack; of: keeping qualities is a serious factor, Particularly inputs of the world where high temperatures are encountered. For this reason, many careful photographers, especially ins'ummer time orin the tropics, keep thecom' ponents oftheir fixingbaths insol id form and makeup fresh fixing solutions each time any photographic material is processed. 1 e v V a n i According to the present invention, preserva tives areintroducedtoproduce a bath or solution which keeps practically indefinitely without detcornposition even at elevated" temperatures and v e can therefore be used even in the tropics andgiif necessary, can be shipped in solution form. 1 The present invention is applicable both to theqordinarywtype using potassium alumaswa gelatin hardening or tanning agent, and to-xthoseqwhich use potassium chrome alum. In the latter case, the stability is even more remarkable astit had been considered up to the presentutime that chrome alum fixing baths could not be kept in so-j lution form for more than a few hours, or at most a day or two, without decomposition; In fact, the

The present invention depends primarily on the employment of citric or tartaric acids advantageously in ccnjunction with small amounts of sodi- 1 55 um phosphate and preferably in the presence of No Drawing.jiApplication Julyf15, 1938. 1 S er ial No.u219,351 i colloidal or finely precipitatedisultur and'as isoon GarnetPhilip Ham,-Ol1i:Greenwich;Connn asp v Signor toAmerica n Cyanamid Company, New York,N.-Y., a corporation of Maine p (ones-4Y5) sodium or other alkalinemetalacetates as abufier. While good results can be obtained' withthese preservatives alone, even better stability is ob- :tained bythe addition of a-fsmall amount of a protective colloid suclr'as coagulable albumen with aismall amount of benzoic acid as apreservative; Thepresence 011a colloid still further inhibits any tendency to precipitation of sulfur. It is an advantage of the present invention that t it may befiused with the usual sodium thiosulfate or other? alkali met'al thiosulfates; or it may .be employed with guanidine thiosulfate fixers where the extraordinary fixing speed of the guanidine thiosulfate justifies its higher price i as in certain casesof tropical processing and newspaperwork, very short fixing times are necessary. The stability producingefiect of the present invention is e PATENT equally applicable tobot h types of fixing procedures. v e

While it is a particular advantage of the" presentinvention'that the fixing bath may e kept in solution form, it iskadvantageous to market prepared fixing powders in solid form, and the ingregdients entering into the fixer of th? prese t in- Evention lend themselves readily tovthis me thod oi wjdis'tribution as they dissolve readily in water. When packaged in solidforin, the ingredients are preferably divided into two powders. The invention will be described in detail incon rejunction with the following specific examples iwhich will describe packaged fixers ofv the presle'nt invention and also the preparation of fixing isolutions therefrom. It should be understood thatvtheexamplesaremerelytillustrations of the invention which is not limited to the exact proportions setfforth as these are not critical which is e further advantage of the invention, permit- Extreme 1 powders are preparedas follows: e

Powde'r A t i 1 v .i Grams :Sodium thiosuli'ate j 222.7

sodium; sulfite, des e 15; 36 Sodium acetate 17;

mdere t Grams Potassium aluminumsulfateu 23.8

Sodium sulfite,des 0. l8 Citric acid 10. 66 Sodium acid phosphatenne 0.81

Powder A is the fixer proper and Powder B, the

' when compared with a solution of Eastman.

Kodak F-5 at 120 F., the solution of Example 1 acid hardening component containing the stabilizing and preserving acid. When it is desired to prepare a fixing bath, Powder A is first dissolved in a liter of water at normal room temperature which will result in some lowering of the solution temperature due to the cooling resulting from the negative heat of solution of the 'thiosulfate. After Powder A has been entirely dissolved, which takes place rapidly if thorough stirring is employed, Powder B is added and thoroughly stirred in. The pH of the resulting solution is,

approximately 4.4. The solution fixes photographic material, and is in every way equal in 1 its fixing and hardening powers to standardfixing' solutions such as for example the'Eastman..

F.5 solution. However, the stability of the solution is very much greater. Thus, for example,

shows no precipitation of sulfur even after hundreds of hours, whereas the standard solution using acetic acid as the acid shows extensive decomposition witha heavy precipitation of sulfur and is unsuitable for usein film fixation. After hundreds of hours at 120 F., the solution of Ex ample 1 shows no perceptible loss of fixing power and gives excellent results with both film and paper. I When kept at temperatures of 6 C. for, extensive periods of time, no sulfurization takes place and the fixing power is unaltered.

ExAMPrJE 2 A-fixing solution is prepared as inExample l, but 1 gram of coagulable albumen and 0.5 gram of benzoic acid are added. This solution gives excellent results and shows even greater stability.

EXAMPLE 3 A chrome alum fixer is prepared in the formof two dry powders as follows:

Powder A v 1 i Grams Sodium thiosulfate 2 22.7 Sodium sulfite, des 30.7 Sodium acetate 17.9

Powder B Grams Potassium chrome a1um 20.0 1 Sodium sulfite, des 0.36 Citric acid; 21.30 Sodium phosphate; -1 12.0

A solution was prepared by dissolving Powder A completely in 500 cc. of water, to which solution Powder B is" then added and completely dissolved. The pH of the resulting solution is about 3.65. The solution is an excellent fixerof the chrome alum type and shows extraordinary stability when tested against a standard Eastman F-5 fixer. When compared at 120 F., the F-5 solution showed heavy decomposition' and precipitation of sulfur at approximately hours,

whereas the solution of Example 3 showed substantially no decomposition even after a period well'in excess of hours and maintained its fixing .power.

If desired, even greater stability can be obthe following:

tained by the addition of 1 gram of sodium metasilicate.

' Exam? 4 i A fixer was prepared as described in Example 1 except that guanidine thiosulfate was substituted for sodium thiosulfate. This fixerhas to be used with considerable care as 'its lfixing speed is sevsodium thiosulfate and unless care is taken and v the photographicmaterial removed from the fixing bathpromptly after. fixation (is complete, re-

' ticulation and some loss of developed image will a result The guanidine' thiosulfate fixer, which is useful for work at higher temperatures and for other high speed fixing operations such as news- 1 i eral times as fast as that of the corresponding paper work, shows primarily, thesame stability as with sodium thiosulfate, showing no decoma position after standing for morethan100 hours at F. I do not claim in this application the use of guanidine thiosulfate generally as a fixer, I

this forming thesubject matter of a copending application of Robe'rtBowling Barnes,-Serial No.

264,975 filed March 30, 1939,"th"e use of 'guanidine thiosulfate being claimed here only in conjunction with the composition of the present inven-, tion.

What I claim is: 1. A photographic'fixing solution the following:

comprising Y Grams Sodium thiosulfate about 223 Sodium sulfite about 16 Sodium acetate about 18 Citric acid about 11 An alum about 20-24 Water sufiicient to make about 1Iliter of solution. 2. A photographic fixing solution of substantially the following composition:

Grams Sodium thiosulfate about 223 Sodium sulfite about 16 Sodium acetate about 18 Citric acid about 11 An alum -r. about 20-24 Sodium acid phosphate. about 1 Water sufficient to make about 1 liter of solution.

3. A photographic fixing solution comprising i s Grams Sodium thiosulfate about 223 Sodium sulfite about 16, Sodium acetate about 18 'Citric acid about 11 Potassium aluminum sulfate about 24- Water sufficient-to make about 1 literof solution;

45A photographic fixing solution having substantially the following composition:

I s Grams Sodium thiosulfate about 223 Sodium sulfiteu about 31 Sodium acetate; about 18 Citric acid about 22 Potassium chrome alum about 20 Sodium phosphate about2 Water sufficient to make about 500 cc. of solution.

GARNET PHILIP HAM.